High tension metal clad switches including plug and socket contacts for eliminating strong electrical field concentrations

ABSTRACT

In a metal clad switch for high voltage comprising cooperating contacts to close and to open the circuit, of which one of said contacts is a bushing contact, the provision of a movable metal disc in the cavity of said bushing contact, said disc being forced by a spring in a position, in which it lies flush with the edge of said cavity, when the switch is in its open condition in order to eliminate the unfavourable influence of the edge of said cavity on the electric field set up in the switch when the latter is alive.

United States Patent Boersma et al. I

HIGH TENSION METAL CLAD SWITCHES INCLUDING PLUG AND SOCKET CONTACTS FOR ELIMINATING STRONG ELECTRICAL FIELD CONCENTRATIONS Rintje Boersma, Hannelen; Gijsbert Waldemar Irk, Bilthoven, both of Netherlands Assignee: N.V. COQ, Utrecht, Netherlands Filed: Aug. 28, 1970 Appl. No.: 67,921

Inventors:

Foreign Application Priority Data Nov. 5, 1969 Netherlands ..6916683 U.S. Cl. ..200/163, 174/73, 200/48 R,

200/166 BF Int. Cl. ..H01h 31/32, HOlh 33/24, H01h 1/38 Field of Search ..200/163, 148 B, 48 R, 148 R,

ZOO/151,150 R, 166 BF;174/73, 127

[151 3,657,504 [451 Apr. 18,1972

[56] References Cited UNITED STATES PATENTS 2,298,859 10/ 1942 Allan et a1 ..200/ 148 R 3,110,791 11/1963 Aspey et a1. ....200/148 X 2,813,179 11/1957 Rugg ..200/163 FOREIGN PATENTS OR APPLICATIONS 592,265 10/1930 Germany ..200/ 151 Primary Examiner-Robert K. Schaefer Assistant ExaminerRobert A. Vanderhye Attorney-Snyder and Butrum [5 7] ABSTRACT 1n a metal clad switch for high voltage comprising cooperating contacts to close and to open the circuit, of which one of said contacts is a bushing contact, the provision of a movable metal disc in the cavity of said bushing contact, said disc being forced by a spring in a position, in which it lies flush with the edge of said cavity, when the switch is in its open condition in order to eliminate the unfavourable influence of the edge of said cavity on the electric field set up in the switch when the latter is alive.

7 Claims, 3 Drawing Figures PATENTEUAPR 18 1912 INVENTOR FIG.2

ATTORNEY HIGH TENSION METAL CLAD SWITCHES INCLUDING PLUG AND SOCKET CONTACTS FOR ELIMINATING STRONG ELECTRICAL FIELD CONCENTRATIONS The invention relates to a metal clad switch for high voltage, comprising at least one bushing contact and an axially movable switching rod cooperating therewith, said switching rod penetrating partly the cavity of said bushing contact, when the switch is in its closed condition.

If such a switch is in the open condition a strong concentration of the electric field set up between the bushing contact and the earthed metal envelope of the switch occurs at the edge region surrounding the entrance of the cavity of the bushing contact. Said concentration can be dangerous for the insulation from earth and requires a greater insulating distance between the bushing contact and the envelope than in the case, in which the switch is closed. Especially in isolator switches, in which the fixed contacts are mounted in borings of spherical junction bodies which are concentrically placed in spherical parts of the envelope, the disturbance of the field by the edge of the open cavity of the bushing contacts can eliminate the advantage of the small insulating distance left between the junction bodies and the envelope and made possible by the spherical shapes.

The invention has for its object to provide a switch, especially an isolator switch, in which the disadvantage referred to is avoided. It is to be seen in that provided in the cavity of the bushing contact is a spring loaded movable metal disc adapted to move in a direction at right angles to its plane and held, in the open condition of the switch, by said spring and a stop member in a position, in which it forms with its surface facing the switching rod a continuation of the edge surface of said cavity and nearly closes the latter, and, in the closed condition of the switch, by the switching rod in a place located deeper within said cavity. Due to said disc the bushing contact or the body, in which the bushing contact is mounted, obtains a nearly uninterrupted surface when the switch is in its open position.

Preferably the switch is constructed in such a manner that at least in the open condition of the switch the disc is electrically conductively connected with the bushing contact and in the closed condition of the switch the current part from the switching rod through the disc to the bushing contact is interrupted by an insulating part. In that case the disc has the potential of the bushing contact when the switch is in its open condition but there will not be produced a parallel current path in the bushing contact through the disc, when the switch is closed. At the occurrence of a short circuit current through the closed switch such a parallel current path, which is unsuitable to conduct current, can lead to serious disturbances.

In order to cope therewith the disc may have a smaller diameter than the cavity of the bushing contact and may be mounted for movement over a metal rod extending in the axis of the cavity and electrically conductively connected with the bushing contact, said rod being provided at its free end with a stop flange and in the place, in which the disc is located in the closed condition of the switch, with an insulating layer, whereas the spring may contact at least with one of its ends an insulating layer. However, it is also possible to provide the disc with a layer of insulating material on its surface facing the switching rod.

The invention will be further elucidated with the aid of the drawing. The latter shows in:

FIG. 1 an axial sectional view of a part of an isolator switch in its open condition, the bushing contact thereof being constructed in accordance with the invention,

FIG. 2 the isolator switch shown in FIG. 1, when it is in its closed condition and FIG. 3 an axial sectional view of a variant of the bushing contact shown in FIGS. 1 and 2, when the isolator switch is in its closed condition.

In the drawing an electrically conductive spherical junction body for the connection of a bus bar 2 to an isolator switch is designated by 1. The spherical junction body is insulatedly and centrally mounted in a metal envelope 3 which is to be connected with earth and has, in the region of said body, a spherical inner wall.

The junction body I is provided with a radial cavity 4, in which fixed annular contacts 5 are provided. These annular contacts 5 cooperate with the axially movable switching rod 6 of an isolator switch. Consequently, the junction body I with the cavity and the annular contacts 5 form together the fixed bushing contact of said isolator switch.

Mounted in the cavity 4 is a metal disc 7 adapted to be moved at right angles to its plane over a composite rod extending in the axis of said cavity and consisting of a bushing 10 of insulating material which is connected by a central bolt 8 to a metal cup 9 fixed to the bottom of the cavity 4 and of a coaxial metal bushing 11 provided with a stop flange 12. Mounted between the cup 9 and the disc 7 is a spring 13 which is insulated from the cup 9 by a ring 14 of insulating material.

In the open condition of the isolator switch (FIG. 1) the disc 7 lies with its surface facing the switching rod flush with the plane through the end of the cavity 4, so that the disc 7 forms a continuation of the surface of the junction body 1. The disc 7, of which the diameter is smaller than that of the cavity 4, is then electrically conductively connected with the junction body 1 through the bushing 11, the bolt 8 and the cup 9, so that it has the same potential as the body 1. Then, the edge of the cavity 4 cannot affect the electric field.

If the switch is closed (FIG. 2) the disc is located deeper within the cavity 4 and it surrounds the insulating bushing 10. Due thereto it is prevented that a parallel current path extending between the fixed contact 1, 5 and the switching rod 6 is set up through the cup 9 and the disc 7. Such a parallel current path is unsuitable to conduct large currents and therefore could lead to serious disturbances, should a short circuit occur.

In the variant shown in FIG. 3 the rod 15, on which the disc is movably mounted, is integral with the cup 9 and the stop for the disc is formed by the head of a bolt 16. The surface of the disc 7 facing the switching rod 6 is provided with a thin layer of insulating material 17, so that there cannot be any metal contact between the disc 7 and the switching rod.

What we claim is:

l. A metal clad switch for high voltage comprising at least one bushing contact, a cavity provided in said contact, an axially movable switching rod cooperating with said bushing contact and extending partly in said cavity when the switch is in its closed condition, a movable metal disc provided in said cavity of the bushing contact and adapted to move in the direction of the axis of the switching rod and at right angles to its plane, a spring forcing said disc towards the open end of said cavity, a stop member, said spring and said stop member holding said disc in a position, in which it lies with its surface facing the switching rod substantially flush with the edge plane of said cavity and substantially closes said cavity, when the switch is in its open position, said disc being held by the switching rod in a place located deeper in said cavity, when the switch is in its closed position, and at least one insulating member which so cooperates with said disc as to interrupt, at least in the closed condition of the switch, the electrically conductive path extending between the switching rod and the bushing contact through said disc.

2. A metal clad switch as claimed in claim 1, in which the metal disc has a smaller diameter than the cavity of the bushing contact and in which the switch comprises in addition a metal guiding rod extending in the axis of said cavity and being electrically conductively connected with the bushing contact, a stop flange formed at the free end of said guiding rod, said disc being adapted to slide on said guiding rod, an insulating layer provided on said guiding rod only in the region thereof, where the disc is found, when the switch is in its closed condition and at least one other insulating layer on which the spring with one of its ends abuts.

3. A metal clad switch as claimed in claim 1, in which the metal disc has a smaller diameter than the cavity of the bushing contact and in which the switch comprises in addition a metal guiding rod extending in the axis of said cavity and being electrically conductively connected with the bushing contact, a stop flange formed at the free end of said guiding rod, said disc being adapted to slide on said guiding rod, and a layer of insulating material provided on the surface of the disc facing the switching rod.

4. In a metal clad switch for high voltage circuits, said switch including:

an electrically conducting body having a cavity; an electrically conductive switching rod movable between an open position in which it is spaced from said body and a closed position in which it projects partially into said cavity in electrical contact with said body; an earthed electrically conductive envelope enclosing said body and said switching rod whereby a strong concentration of electric field tends to set up between the edge region of said body surrounding said cavity and said envelope when said switching rod is in its open position; means for eliminating said strong concentration of electric field and including a metal disc disposed in said cavity, a rod fixed to said body and projecting axially within said cavity to guide said disc and having at least an exposed end portion which provides a stop for said disc and which is in electrical connection with said body, and means for normally urging said disc into engagement with said stop to position said disc substantially flush with said edge region of said body when said switching rod is in its open position and to allow said disc to be pushed into said cavity by said switching rod when the latter is moved to its closed position;

and insulating means for eliminating a current path through said switching rod and said disc to said body when the switching rod is in its closed position.

5. In a metal clad switch as defined in claim 4 wherein said body is spherical and said envelope presents a spherical inner wall within which said body is concentrically disposed.

6. In a metal clad switch as defined in claim 4 wherein said insulating means comprises a layer of insulating material on that side of said disc facing said switching rod.

7. In a metal clad switch as defined in claim 4 wherein said rod is provided with an integral metal cup bottomed within said cavity, said insulating means comprises an annular member of insulating material seated upon said cup and a bushing of insulating material surrounding said rod adjacent said cup, and said means for urging said disc comprises a spring disposed between said disc and said annular member of insulating material. 

1. A metal clad switch for high voltage comprising at least one bushing contact, a cavity provided in said contact, an axially movable switching rod cooperating with said bushing contact and extending partly in said cavity when the switch is in its closed condition, a movable metal disc provided in said cavity of the bushing contact and Adapted to move in the direction of the axis of the switching rod and at right angles to its plane, a spring forcing said disc towards the open end of said cavity, a stop member, said spring and said stop member holding said disc in a position, in which it lies with its surface facing the switching rod substantially flush with the edge plane of said cavity and substantially closes said cavity, when the switch is in its open position, said disc being held by the switching rod in a place located deeper in said cavity, when the switch is in its closed position, and at least one insulating member which so cooperates with said disc as to interrupt, at least in the closed condition of the switch, the electrically conductive path extending between the switching rod and the bushing contact through said disc.
 2. A metal clad switch as claimed in claim 1, in which the metal disc has a smaller diameter than the cavity of the bushing contact and in which the switch comprises in addition a metal guiding rod extending in the axis of said cavity and being electrically conductively connected with the bushing contact, a stop flange formed at the free end of said guiding rod, said disc being adapted to slide on said guiding rod, an insulating layer provided on said guiding rod only in the region thereof, where the disc is found, when the switch is in its closed condition and at least one other insulating layer on which the spring with one of its ends abuts.
 3. A metal clad switch as claimed in claim 1, in which the metal disc has a smaller diameter than the cavity of the bushing contact and in which the switch comprises in addition a metal guiding rod extending in the axis of said cavity and being electrically conductively connected with the bushing contact, a stop flange formed at the free end of said guiding rod, said disc being adapted to slide on said guiding rod, and a layer of insulating material provided on the surface of the disc facing the switching rod.
 4. In a metal clad switch for high voltage circuits, said switch including: an electrically conducting body having a cavity; an electrically conductive switching rod movable between an open position in which it is spaced from said body and a closed position in which it projects partially into said cavity in electrical contact with said body; an earthed electrically conductive envelope enclosing said body and said switching rod whereby a strong concentration of electric field tends to set up between the edge region of said body surrounding said cavity and said envelope when said switching rod is in its open position; means for eliminating said strong concentration of electric field and including a metal disc disposed in said cavity, a rod fixed to said body and projecting axially within said cavity to guide said disc and having at least an exposed end portion which provides a stop for said disc and which is in electrical connection with said body, and means for normally urging said disc into engagement with said stop to position said disc substantially flush with said edge region of said body when said switching rod is in its open position and to allow said disc to be pushed into said cavity by said switching rod when the latter is moved to its closed position; and insulating means for eliminating a current path through said switching rod and said disc to said body when the switching rod is in its closed position.
 5. In a metal clad switch as defined in claim 4 wherein said body is spherical and said envelope presents a spherical inner wall within which said body is concentrically disposed.
 6. In a metal clad switch as defined in claim 4 wherein said insulating means comprises a layer of insulating material on that side of said disc facing said switching rod.
 7. In a metal clad switch as defined in claim 4 wherein said rod is provided with an integral metal cup bottomed within said cavity, said insulating means comprises an annular member of insulating material seated upon said cup and a bushing of insulating material surrounding said rod adjacent said cup, and said means for urging said disc comprises a spring disposed between said disc and said annular member of insulating material. 